Advanced miniaturization of semiconductor elements is demanding higher standards for deposition characteristics. For example, a gate insulating film is requested to be very thin. A thin electrode film or the like needs to be stably formed on a very thin insulating film. Also, the impurity level needs to be decreased because an impurity such as carbon in a film or at the interface between thin films affects the element performance.
A sputtering method used as one of deposition methods can achieve high-quality deposition because the raw material does not contain an impurity such as carbon, unlike a CVD method. The sputtering method is useful because it does not use a hazardous organometallic material, unlike CVD, and need not execute abatement processing for a by-product and virgin raw material.
For example, in a sputtering deposition method of depositing a thin film on a substrate made of silicon or the like (to be referred to as a “substrate”), a target holder in an evacuated vacuum chamber holds a vapor deposition source called a target made of a material to be deposited on a substrate. A substrate holder in the vacuum chamber supports the substrate. Gas such as Ar is introduced into the vacuum chamber, and a high voltage is applied to the target, generating a plasma. According to the sputtering deposition method, the target material is attached to the substrate supported by the substrate holder using the sputtering phenomenon of the target by charged particles in the discharge plasma. In general, positive ions in the plasma enter a negatively charged target, sputtering atoms and molecules of the target material from it. These atoms and molecules are called sputtered particles. The sputtered particles attach to the substrate, forming a target material-containing film on the substrate.
In the sputtering deposition apparatus, a freely openable shield plate called a shutter is generally interposed between a target and a substrate. With this shutter, the timing to start deposition is controlled not to start deposition processing until the plasma state in the vacuum chamber is stabilized. More specifically, the shutter is closed not to deposit a film on a substrate until a plasma generated by applying a high voltage to a target is stabilized. After the plasma is stabilized, the shutter is opened to start deposition. By controlling the start of deposition using the shutter in this way, a film can be deposited on a substrate with good controllability using the stable plasma, so a high-quality film can be deposited.
A plasma processing apparatus disclosed in patent reference 1 includes, in a vacuum chamber, a wafer holder having a plate for supporting a wafer and a plurality of wafer lift pins, a moving shutter which moves parallel to a wafer, and a shutter storage unit for storing the moving shutter while a substrate is processed using a plasma.